[PATCH v3 3/6] iomap: split size and error for iomap_dio_rw ->end_io

Matthew Bobrowski
2019-09-12T11:04:24Z

Modify the calling convention for the iomap_dio_rw ->end_io() callback.
Rather than passing either dio->error or dio->size as the 'size' argument,
instead pass both the dio->error and the dio->size value separately.

In the instance that an error occurred during a write, we currently cannot
determine whether any blocks have been allocated beyond the current EOF and
data has subsequently been written to these blocks within the ->end_io()
callback. As a result, we cannot judge whether we should take the truncate
failed write path. Having both dio->error and dio->size will allow us to
perform such checks within this callback.

Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
[hch: minor cleanups]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---

Note, this patch is already queued in the 'iomap-5.4-merge' branch here:
https://git.kernel.org/pub/scm/fs/xfs/xfs-linux.git/log/?h=iomap-5.4-merge.

Just adding it within this patch series to highlight that it's a
dependency.

fs/iomap/direct-io.c | 9 +++------
fs/xfs/xfs_file.c | 8 +++++---
include/linux/iomap.h | 4 ++--
3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 10517cea9682..2ccf1c6460d4 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -77,13 +77,10 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
loff_t offset = iocb->ki_pos;
ssize_t ret;

- if (dio->end_io) {
- ret = dio->end_io(iocb,
- dio->error ? dio->error : dio->size,
- dio->flags);
- } else {
+ if (dio->end_io)
+ ret = dio->end_io(iocb, dio->size, dio->error, dio->flags);
+ else
ret = dio->error;
- }

if (likely(!ret)) {
ret = dio->size;
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 28101bbc0b78..74411296f6b5 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -369,21 +369,23 @@ static int
xfs_dio_write_end_io(
struct kiocb *iocb,
ssize_t size,
+ int error,
unsigned flags)
{
struct inode *inode = file_inode(iocb->ki_filp);
struct xfs_inode *ip = XFS_I(inode);
loff_t offset = iocb->ki_pos;
unsigned int nofs_flag;
- int error = 0;

trace_xfs_end_io_direct_write(ip, offset, size);

if (XFS_FORCED_SHUTDOWN(ip->i_mount))
return -EIO;

- if (size <= 0)
- return size;
+ if (error)
+ return error;
+ if (!size)
+ return 0;

/*
* Capture amount written on completion as we can't reliably account
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index bc499ceae392..50bb746d2216 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -188,8 +188,8 @@ sector_t iomap_bmap(struct address_space *mapping, sector_t bno,
*/
#define IOMAP_DIO_UNWRITTEN (1 << 0) /* covers unwritten extent(s) */
#define IOMAP_DIO_COW (1 << 1) /* covers COW extent(s) */
-typedef int (iomap_dio_end_io_t)(struct kiocb *iocb, ssize_t ret,
- unsigned flags);
+typedef int (iomap_dio_end_io_t)(struct kiocb *iocb, ssize_t size, int error,
+ unsigned int flags);
ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
const struct iomap_ops *ops, iomap_dio_end_io_t end_io);
int iomap_dio_iopoll(struct kiocb *kiocb, bool spin);
--
2.20.1